Aromatic compounds such as isopropylbenzene, ethylbenzene, butylbenzene and similar compounds have found wide use in many applications and particularly in the production of monomers used in aromatic polymers. Two of the major methods of producing aromatic compounds such as these are the Friedel-Crafts alkylation reaction of aromatic compounds with alkyl halides, alkenes or alkynes and the Friedel-Crafts transalkylation reaction of monoalkyl or polyalkyl aromatic compounds with aromatic compounds. Frequently in industrial practice both of these reactions occur in the same process. The aromatic compound is alkylated to produce mixtures of the monoalkyl aromatic and polyalkyl aromatic compounds. The alkylated aromatics produced during the reaction are transalkylated with unsubstituted aromatic compound to produce additional quantities of desired monosubstituted aromatic compound.
These alkylation and transalkylation reactions are generally catalyzed by a metal halide-based Friedel-Crafts catalyst system which is typically composed of a metal halide containing a hydrogen halide or alkyl halide cocatalyst. The catalyst mixture can be employed in either the solid or liquid phase; the liquid phase is often preferred industrially because it is generally easier to inject into the reactor and easier to regulate. When the liquid phase is employed, a catalyst complex composed of metal halide catalyst, hydrogen halide or alkyl halide cocatalyst, and monoalkyl aromatic and/or polyalkyl aromatic compounds is used. Although this catalyst complex can be formed in situ, it is preferred that the catalyst complex be generated separately and subsequently introduced to the reaction mixture. This is preferable because the catalyst complex can be prepared at a lower temperature than the reaction temperature and thus have a higher activity due to the substantial avoidance, at the lower temperature, of side reactions that lead to compounds that may poison a portion of the catalyst.
As the alkylation or transalkylation reaction proceeds, the catalyst is gradually deactivated and must be regenerated. In the past, regeneration has generally been accomplished by separation of catalyst from the reaction and treatment with regenerative compounds, such as hydrogen chloride, hydrogen, aluminum, aluminum chloride, and some aliphatic hydrocarbons. This separation and subsequent regeneration is costly and time consuming. A further problem encountered is the lessened catalyst activity, resulting in reduced yield, due to the employment of the partially deactivated catalyst. A method of regenerating the catalyst complex which will require less cost than heretofore possible and will improve the catalyst activity would be highly desirable.